1. Field of the Invention
The present invention relates to a projection-type display device, and, in particular, to a projection-type display device having a novel feature of improving a system of combining an image projected and an image drawn thereon by a user.
2. Description of the Related Art
Conventionally, generally, a projection-type display device is applied to a projector, a media board with a display device, a personal computer, etc., is used as a monitor for two or more persons in a meeting, a lecture, etc., or is used as a monitor, such as in a personal computer used individually.
Such a projection-type display device is demanded to have a feature such that letters/characters, and/or pictures may be drawn on a display device in a superimposing manner together with an image projected there, and, also, the thus-drawn letters/characters and/or pictures can be obtained as electronic data.
For this purpose, an art is proposed in which a position of a nib contacted on a display screen is detected, and is traced. However, in order to detect the position at which the nib contacts, it is necessary to provide a special pen with the nib. Furthermore, in order to add/erase a letter/character/picture, it is needed to appropriately change a screen operation mode. Thus, the whole system becomes expensive and operation becomes complex.
Further, another art is disclosed by Japanese laid-open patent application No. 3-43726 in which an image drawn by a nib or the like on a display screen is scanned by a line-type photo-sensor, and, the thus-detected image is printed out. However, as the line-type photo-sensor should have a size corresponding the size of the screen, the scanner should be larger in case the size of the screen is larger. In such a case, as the scanner mechanically scans the screen, a mechanism of moving the scanner also may be of large-sized. Thus, the whole system may become bulky. Also, as the screen is scanned by the scanner mechanically, a considerable time is required to read the whole image present on the screen.
According to a media board disclosed in Japanese laid-open patent application No. 6-347898, while an image printed on a transparent sheet is displayed on a screen, it is possible to draw/write letters/characters/pictures thereon. Further, as a scanner scans the thus-drawn image, the scanned image can be easily printed out, as a hard copy. However, in this art, as the scanner mechanically scans the image present on the screen, the problems same as in the above-mentioned art may occur, i.e., the whole system may become bulky.
According to a so-called optical blackboard disclosed by Japanese laid-open patent application No. 8-160539, as a user points on a screen by a special pen, an image is projected thereon according to a locus along which the user has moved the pen on the screen through a function of a photo-sensing technology or a pressure-sensing technology. In this art, as an image is displayed on the screen as a result of the user moving the special pen on the screen and then the movement being detected by the system, the relatively complex system is needed merely for drawing an image on the screen by the user, in comparison to a case where a user draws an image directly on a screen with ink or the like by using a common ink-used pen as in a common whiteboard.
According to a media board disclosed by Japanese laid-open patent application No. 10-297166, an image drawn on a screen is read electronically, the read image data is combined with another image being projected on the screen. However, no specific configuration of how to read a drawn image is disclosed in the publication.